180 MINUTE STBUCTURE OF THE SEED. 



upland or "short-staple" cotton, a little over one inch and a 

 half (three and three-fourths centimeters). The greatest width 

 of fibre was found to be .0013 inch. A single fibre sustained 

 without breaking a weight of 150 grains. 1 



506. It has been shown in Volume I. that the seed-coats of 

 many Polemoniaceae, etc., are furnished with microscopic hairs, 

 "which come usefully into play in arresting farther dispersion at 

 a propitious time or place. . . . The testa is coated with short 

 hairs, which when wetted burst, or otherwise open and discharge 

 along with mucilage one or more verj- attenuated long threads 

 (spiricles) which were coiled within. These protruding in all 

 directions, and in immense numbers, form a limbus of considera- 

 ble size around the seed, and evidently must serve a useful end 

 in fixing these small and light seeds to the soil in time of rain, 

 or to moist ground, favorable to germination, to which they ma}' 

 be carried by the wind." The best example of this structure is 

 afforded by the genus Collomia ; in this the spiricles are long 

 and very numerous. 



507. The nervation of the seed-coats furnishes in many 

 cases excellent diagnostic characters, but they need no special 

 remark histologically. The forms of branching of the fibro- 

 vascular bundle of the funicnlus indicate that the ovule and 

 seed are of the nature of leaflets on the margin of the carpellary 

 leaf. 8 



1 The above measurements are approximate ; those which follow are the 

 exact determinations as they are given by Professor Ordway in the Tenth 

 Census of the United States. 



Length of fibre. Maximum length found in the "sea-island" variety of 

 South Carolina, where it was 1.996 inches. The maximum length of the 

 upland or "short-staple" cotton was 1.669 inches. The minimum of length 

 (0.695 inch) was found in North Carolina cotton, grown on a light, sandy 

 loam soil. 



Width of fibre. The widest d^W inch wide) was quite short (0.945 inch). 

 By far the largest number of wide fibres come from uplands. The "sea-island" 

 variety had a width of ntthe inch. 



Strength of fibre. The strongest specimen examined had a breaking weight 

 of 149.4 grains. Professor Ordway mentions some instances which lead him to 

 think that the strength of the fibre may hold some relation to the amount of 

 phosphoric acid in the soil where it is grown. 



Weight of seeds and lint. (Maximum weight for five seeds with lint at- 

 tached, 22.14 grains.) Light-weight seeds appear to come from sandy soils, 

 heavy-weight seeds from heavy and productive soils. 



2 The reader is referred to a memoir by Le Monnier, in Ann. des Sc. 

 uat., ser. 5, tome xvi., 1872, p. 233, and one by Van Tieghem in same Journal, 

 1872. 



